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ATEX, the European directive

Standard regulations for equipment used inside hazardous areas with potentially explosive atmospheres is a core issue for the European Union. Thus, they took the lead in developing standards which became famous as ATEX directives (ATmosphèresEXplosibles). They apply to all kinds of, electrical or non-electrical equipment and safety devices as well as machines and industrial facilities located within potentially explosive atmospheres.

Since July 2003 it is mandatory to use devices which have a ATEX type approval all across Europe.

94/9/EC Directive

Harmonises legal provisions of memberstates for devices and protection systemsfor designated use in potentially explosiveareas. ATEX 95

1999/92/CE Directive

Minimum requirements for improving the health and safety protection of the worker at risk from explosive atmospheres. ATEX 137

 

 

Explosion Protection

The important principles for integrated safety explosion protection are as follows:

  • Measures are taken to avoid hazardous atmospheres whenever possible.
  • Measures are taken which prevent the ignition of hazardous atmospheres.
  • Measures are taken which limit the explosive effect to a safe degree.

 

This differs from:

Primary explosive protection

These are precautions taken to prevent or restrict the formation of hazardous explosive atmospheres.

Secondary explosive protection

This covers the second group of measures, which are intended to prevent the ignition of an atmosphere that is capable of exploding.

 

 

Definition is in line with Directive 1999/92/EC (ATEX 137)ReferenceZone according to CENELEC IECRequired equipment categoryRequired identification according to 94/9/EC ATEX95 
Area in which a potentially explosive atmosphere as a mixture of air and flammable gases, vapors or mist is present, either frequently or over a longer period.> 1000 h / a01GG
Area in which under normal operating conditions a potentially explosive atmosphere as a mixture of air and flammable gases, vapors or mists may occasionally form.100 - 1000 h / a12G  (1G also possible)G
Area in which under normal operating conditions a potentially explosive atmosphere as a mixture of air and flammable gases, vapors or mists may occur for only a short period.<10 h / a23G  (1G 2G also possible)G
Area in which a potentially explosive atmosphere in the form of a cloud of flammable air-borne dust is present, either continuously for long periods or frequently.> 1000 h / a201DD
Area in which under normal operation a potentially explosive atmosphere in the form of a cloud of dust in the air can occasionally form.100 - 1000 h / a212D  (1D also possible)D
Area in which under normal operation a potentially explosive atmosphere in the form of a cloud of combustible dust in air is not normally present, although may occur for only a short period<10 h / a223D  (1D 2D also possible)D

 

When do i need ATEX?

The ATEX Directive applies where during normal operation or malfunction of a machine and / or plant explosive atmospheres. Emergencies are not covered. The new Directive (94/9/EC 99/92/EC +) replaces Directives 76/117/EEC and 94/9/EC 82/130/EEG.Richtlijn is intended for the manufacture of the equipment, Directive 99/92 / EC isbedoeld for working in explosive environments (work). The ATEX Directive covers all potential explosive atmospheres which may arise due to gases, vapors, mists or dusts.

Excluded from the ATEX directive are:

Medical environments
Household environments
Non-commercial environments
Ships
Public transport

Besides equipment and protective systems intended for use in potentially explosive atmospheres are also things outside this area under the Directive if they are required voorhet safe operation of the equipment.

When there is a potentially explosive atmosphere? If the correct proportion of oxygen, flammable product and possible ignition source is.Voor an ignition source must be also discharges denken.Een atmosphere is explosive from the LEL to UEL.

Of almost all products can be safety data retrieval, herein you will find all the necessary information such as the LEL, UEL, flash point etc. Also the flash point is a very important criterion. We have below then a portion of two safety data sheets printed on very famous products, namely Acetone and Diesel.

Physical and chemical properties of      ACETONE                       DIESEL                         
Physical state at 20 ° CLiquidLiquid
View colorClear, colorlessLight yellow
OdorIrritantCharacteristic
Boiling58 ° C170 ° C
Melting point-95 ° C 
Flashpoint-19 ° C> 56 ° C
Ignition temperature465 ° C> 250 ° C
Relative vapor density (air = 1)2.0 
Flammability limit (LEL)2.3% (v / v)1% (v / v)
Flammability limit (UEL)13% (v / v)6% (v / v)
Relative density (water = 1)0.8 
Water-solubleCompletely solubleNo data available

 

ProductLEL          UEL             Flashpoint     Application
Acetone2.3%13%-19 ° CDiluent
Diesel1%6%56 ° CFuel for diesel engines
Gasoline (unleaded Euro 95)1%6% - 8%-40 ° CFuel for petrol engines
Ammoniac15%30%GasRefrigerant for refrigeration
Gas5%15.8%GasFuel
Hydrogen4%75%GasGeneral Industrial

 

Definition of "flashpoint"

The lowest temperature at which a liquid fluid, under certain standard conditions so much vapor that is an ontsteekbar vapor / air mixture can be formed. One must take into account in normal atmospheric conditions from a omgevingstemperatuurvan -20 ° C to +40 ° C, 10 ° C math here to reserve one arrives at 50 ° C.In principle, all products from a flash point of 50 ° C or higher as diesel is not explosive dangerous. Of course there are circumstances that still a hazardous explosive atmosphere can be achieved by eg certain production processes (sputtering, etc ...). >

 

Definition of "LEL" and "UEL"

Lower Explosive Limit (LEL): Concentration of flammable gas, flammable vapors or combustible mist in air below which no explosive atmosphere is formed.

Upper Explosive Limit (UEL): Concentration of flammable gas, flammable vapors or combustible mist in air above which an explosive atmosphere is formed.

If a product has an LEL of 15% or more (such as ammonia) will in no danger Outdoor installations be seeded. Indeed, it is not possible that, in practice, higher concentrations may occur over 15% due to the mixing of the outside air. Consequently, an ammonia plant in the open air outside the ATEX Directive, notwithstanding that it is a gas.

 

When do i need to comply with the ATEX Directive?

For products with a lower than 15% LEL and a flash point lower than 50 ° C, one can speak of a potentially explosive atmosphere. In this case one falls under the ATEX directive and one is obliged to make a zone classification according to the applicable guidelines and standards. Also, all materials comply with the ATEX Directive.

 

ATEX zones

Safety is highest priority

At all places where inflammable substances are produced, processed, transported or stored, safety is extremely important - especially in the chemical and petrochemical industry, in oil and natural gas production and in mining.

In order to provide the highest level of safety possible, most states' legislations have developed corresponding conditions in the form of laws, regulations and standards. These now have to be implemented by companies because the operator of a plant is solely responsible for safe operation in accordance with the German Ordinance on Industrial Safety and Health (BetrSichV).

The area of responsibility thereby extends to:

  • Stipulation of the explosive areas (zones),
  • Compilation of an explosion protection document,
  • Realisation of organisational and technical measures for explosion protection,
  • Implementation of checks,
  • Use of products in Ex-areas that comply with the ATEX 95 directive.

Meaning of the zone classification

  • Zone 0/20: Danger is always present, for a long time or frequently
  • Zone 1/21: Danger is occasionally present
  • Zone 2/22: Danger is seldom present or present for a short time

 

Fundamentals of dust explosion protection

Fundamental principles:
The manufacturer of operating devices for areas rendered potentially explosive through dust must indicate the maximum surface temperature of all devices that dust can penetrate (usually expressed in °C - indication of the temperature class should be avoided here). This temperature is part of the dust Ex-designation.

Designation examples:
II 2D T90 °C IP64, II 2D Ex td A21 T90 °C IP64
(If the ignition protection type is based on the housing, the housing protection rating should also be stated as an IP Code)

or II 2D Ex iaD 21 T96 °C
(This device has already been approved according to the new IEC de-jure standard "Intrinsic Dust Safety - iaD". This de-jure standard specifies that the designation also contains the corresponding zone - in this case 21)

Dust explosion protection - temperature:
Combustion and explosion parameters for dusts depend on the their condition. Parameters that affect combustion and explosion behaviour include particle size, particle shape, water content, purity and where applicable the content of the flammable solvents.
The particle size distribution and the mean value (value for average particle size) should also be known.

In accordance with 1999/92/EG Directive (ATEX 137, replacing: ATEX 118a),the system operator /employer is obliged to make a hazard assessment and must therefore be aware of the minimum glow temperature of the dust.

There are simple calculations to determine the two "temperatures" and they are carried out thus:

  1. Limit temperature 1 = 2/3 of minimum ignition temperature
  2. Limit temperature 2 = minimum ignition temperature* minus 75 °K

These two limit temperatures must now be examined to confirm which guarantees the greater safety.

Example 1:
Minimum ignition temperature = +330 °C,
Limit temperature 1 = 2/3 x +330 °C = +220 °C
Limit temperature 2 = +300 °C - 75 °K = +225 °C

Greater safety: Limit temperature (1) = +220 °C
Here a device with a max. surface temperature in the event of failure <= +220 °C must be used. As stated, the device designation includes a corresponding value.

 

Example 2:
Minimum ignition temperature = +186 °C,
Limit temperature 1 = 2/3 x +186 °C = +124 °C
Limit temperature 2 = +180 °C - 75 °K = +105 °C

Greater safety: Limit temperature (2) = +105 °C
Here a device with a max. surface temperature in the event of failure <= +105 °C must be used.

 

*The value for the glow temperature applies with a dust layer thickness of 5mm. The temperature safety distance must be increased for larger layer thicknesses.